Rotatable bodies referred to herein as "rotors" to be balanced are conventionally mounted or supported in balancing machines by support rollers or by a support spindle. Antifriction bearings or slide bearings are used to mount the support rollers or the support spindle in the balancing machine.
If it is necessary to balance or control rotors that are rotating at an r.p.m. close to their critical revolutions per minute, which could cause the system of the rotor and its support structure to resonate, measures are necessary which avoid dangerous resonant amplifications. Simultaneously it is necessary to keep the system of the rotor and its support structure free of any imposed or undesired constraining forces.
According to German Patent Publication DE-OS 2,141,502, corresponding to U.S. Pat. 3,754,801 (Giers et al.), issued on Aug. 28, 1973, it is known to equip a balancing machine so that it permits changing the resonance frequencies of the system formed by the rotor and its support structure. The conventional construction makes it possible to vary the resonance frequencies of the system in such a way that passing of the system through resonance peaks is avoided. More specifically, the resonance frequencies are controlled so that resonance peaks are avoided during a test sequence. For this purpose the above mentioned disclosure of the German and corresponding U.S. Pat. 3,754,801 provides for additional supports one end of which is rigidly secured to the machine foundation in a force transmitting, formlocking or positive manner while the other end of the additional supports is connected to a support housing through a friction coupling that is remote controllable for temporarily detuning the system of the rotor and its support structure formed by support rollers or a support spindle mounted in the support housing. However, the need for the additional supports makes the known balancing machine involved and hence expensive.